Dave,Experts will probably contribute, but here is an amateur's experience. There are lots of youtube videos on taking Weihrauchs apart and putting them back together. A fellow named Tom Gaylord writes a blog and some other things about working on air rifles. I found him a good source. Search for him on Pyramyd Air site. People on GTA are extremely helpful. I might still be trying to assemble a Diana trigger without advice.I found unscrewing the HW80 cap was a challenge. Had the parts, lubes, needle files, misc smithing tools and home-made compressor. I just failed at removing the screw cap. Now plenty of pros and experienced folks will have ideas. Maybe their techniques work for you. Tried most of them. I finally gave up and sent mine to John Thomas (John in PA). Yeah, defeat and all that is bitter. On the other hand, John's work was terrific. Thousands of pellets later still extremely accurate. Second chapter, I did get to use my tools and enthusiasm on another Weihrauch (50S) and Diana 24. Got nice improvements, but nothing like John's professional job. 50S on third experimental spring. D24 parts scarce. John covered all those vagaries.So if you want a project and are not particular about the results (like my 50S), give it a try. Ordering parts, puzzling over why its so hard to cock, looking for pivot bolts, searching the floor for little springs may be your cup of tea. If, however, you just want a great shooter and can handle the freight, any professional tuner surely exceeds my ability. After I tune 50 rifles, maybe I can approach a real tuner's ability. JumpinWelcome to GTA. Plenty of room and fellow travelers here for tinkerers, tuners, and shooters.
I can help you out when ever you ready to do some tuning, I have tuned a bunch of R1's over the yrs, just send me a pm and I'll shoot you my PH# and go from there!!!
Mark has spoken wisely about the ARH kits,I have some pictures of a brand new HW 80 Mk1 in .177 I purchased not too long ago, and rebuilt it. It was a time capsule from a collection. Here are some of the pics as I went through it,